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C00002 00002	@make(letterhead,Phone"497-4430",Who"John McCarthy",Logo Old, Department csd)
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@make(letterhead,Phone"497-4430",Who"John McCarthy",Logo Old, Department csd)
@style(indent 8)
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@begin(address)
Professor Ralph W. Lewis
Department of Natural Science
Michigan State University
East Lansing, Michigan 48824
@end(address)
@greeting(Dear Professor Lewis:)
@begin(body)
	I too have pondered the problem of implicit premisses, which
is at least as important in common sense reasoning as in formal
scientific reasoning.  Circumscription (see enclosed) is intended
to deal with at least part of this problem by formalizing an
approximate version of Ockham's razor.  The idea is that certain
predicates are assumed to have minimal extension compatible with
the premisses that have been assumed about them.

	Whether this formal device can be made to cover a substantial
part of common sense or scientific plausible and implicit reasoning
remains to be seen.
@end(body)
Sincerely,




John McCarthy
Professor of Computer Science